J. Julien

Subthreshold K+ production in heavy ion collisions☆

Abstract The cross section for K+ meson production in collisions of 36Ar ions on a 48Ti target has been measured at an incident energy of 92 MeV per nucleon. A description of the experimental set-up is given. Twelve events attributed to monoenergetic muons following the decay of stopped kaons have been identified. From these events, one infers a production cross section of 240 pb. Data are briefly discussed.

Linear momentum transfer in pion accompanied 16O induced reaction on 232Th at 95 MeV per nucleon

Abstract Positive pions and protons emitted at 90° were measured in coincidence with two fission fragments in the reaction 16 O + 232 Th at 95 MeV/nucleon. The linear momentum transfer distribution has been determined from the folding angle between the fragments. The average momentum transfer is 2.5 GeV/ c ± 0.2 GeV/ c for a pionic reaction. An analysis in terms of impact parameter distributions leads to the conclusion that subthreshold pion production requires a large overlap of projectile and target density profiles.

Kaon production in nucleus - nucleus collisions at 92 MeV per nucleon

Abstract The cross sections for K + meson production in collisions of 36 Ar on 12 C, nat Ti and 181 Ta at an incident energy of 92 MeV per nucleon have been measured. A description of the set-up and of the method is given ; it is based on measurement of the muon decay of the positive kaon. At such a low incident energy the K + production seems to be more sensitive to the available energy in the center of mass of the nucleus-nucleus system than to the coulomb corrected incident energy normalized to the production threshold in a free nucleon-nucleon process.

Search for an enhanced production of low energy pions in C(p, π+)X, Cu(p, π+)X, and Cu(p, π∘)X reactions for 300 MeV≦Tp≦400 MeV

The observation of an enhancement in the production of low energy pions in the Cu(p, π+)X reaction is confirmed. The width of the bump is about 5 MeV around 350 MeV. A similar enhancement appears at 330 MeV for C(p, π+)X but the width has not been measured. An attempt to observe this behaviour in Cu(p, π∘)X is described. From the data one cannot conclude about the existence of a structure around 350 MeV proton energy. The lack of resolution in theπ∘ spectrometer may have washed out the small effect expected fromπ+ measurements.

Heavy ion collision geometry at 93 MeV/u from π−π+ measurement

Abstract Low momentum pion production is measured at an angle of 0° in 16O induced reactions. Strong Coulomb effects on the ratios π − π + are observed. Charge distributions of reaction products are extracted. Pions are produced by an intermediate system whose charge and velocity are given in agreement with the participant zone predicted in a simple geometrical participant-spectator picture. Effects due to projectile fragments are also observed, and are dominant in light mass systems.

Neutral pion production in subthreshold heavy ion collision with16O (38 MeV/u) and20Ne (200 MeV/u) beams

Inclusive production of neutral pions has been studied in16O +27Al,197Au reactions at 38 MeV/u and20Ne +27Al reaction at 200 MeV/u. A setup of 10 Pb glass Cherenkov detector telescopes was used to detect the twoγ rays from theπ0 decay.

π− Production in16O +27Al at 38, 65 and 93 MeV/u

Negative pion production cross-sections are measured at 38, 65 and 93 MeV per nucleon in O + Al reaction. Rough estimations of the total cross sections are given and compared to previous neutral pion data. Double differential cross sections at 93 and 65 MeV/u show enhancement for pions with velocity close to the beam. At variance no effect is observed at 38 MeV, where π− and π0 distributions are identical. Fewπ+ detected at 38 MeV support this result. This indicates that at the lowest incident energy nearly the whole projectile participates in the production reaction.

New limit in the search for spontaneous pion emission from252Cf source

AbstractA new experiment was carried out at Modane (Laboratoire Souterrain de Modane, France) to determine the ration

Kaon production in nucleus-nucleus collisions at 92 MeV per nucleon

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